Spiraled strip material having parallel grooves forming plurality of electron multiplier channels



July 7,1970 A.o..1':-:Ns:-:N 3,519,870

' Filed May 18, 196

SPIRALED STRIP MATERIAL HAVING PARALLEL GROOVES FORMING PLURALITY 0FELECTRON MULTIPLIER CHANNELS a 4 Sheets-Sheet l Fewer Kai/w I July 7,1970 A o. JENSEN I 3,519,870

SPIRALED STRIP MATERIAL HAVING PARALLEL GROOVES FORMING PLURALITY OFELECTRON MULTIPLIER CHANNELS Filed May 18, 196' 4 Sheets-Sheet 2 "July1, 19,70

Fiied lay 1a, 196' OJENSEN 3,5l,870

A. SPIRALED' STRIP MATERIAL HAVING PARALLEL GROOVES'FORMING PLUR'ALITYOF ELECTRON MULT'IPLIER CHANNELS 4 Sheets-Sheet 5 July 7, 1970 A. O JENSSPIRALED STRIP MATERIAL HAVING PARALLEL GROOVES FORMING Filed May 18,196' PLURALITY OF ELECTRON MULTIPLIER CHANNELS 4 Sheets-Sheet 4 Vapara/ef/ecfra de dr/l/j'e flea/rode for GM/rafled r ei/fffl f/y 4/71/12 0.Jam? United States Patent 3,519,870 SPIRALED STRIP MATERIAL HAVINGPARALLEL GROOVES FORMING PLURALITY OF ELECTRON MULTIPLIER CHANNELSAndrew 0. Jensen, Arcadia, Califl, assignor, by mesne assignments, toXerox Corporation, a corporation of New York Filed May 18, 1967, Ser.No. 639,555 Int. Cl. H013 43/20, 43/24 US. Cl. 313-105 2 Claims ABSTRACTOF THE DISCLOSURE This invention relates to an electron multiplier.Generally, the electron multiplier of the present invention isconstructed from a plate of insulating material. The plate of insulatingmaterial contains a plurality of parallel grooves on at least onesurface of the insulating plate. A layer of secondary emission materialcovers the walls of the grooves so that the plurality of groovesprovides for a plurality of electron channels. A plurality of groovedplates of insulating material or a single spiraled plate may be used toprovide for a two-dimensional electron multiplier.

multipliers of the prior art. In addition, the electron multiplier ofthe present invention allows for a reduction in cost over prior artelectron multipliers.

As indicated above, the electron multiplier of the present inventionincludes a plate of insulating material which contains a plurality ofgrooves coated with secondary emission material. In the use of theelectron multiplier of the present invention, electrons are introducedat a first side of the grooved plate and the electrons move down thelength of the grooves and strike the secondary emission material atprogressive positions along the grooves. Ultimately the electrons emergeat a second opposite side of the plate and there is a multiplication ofthe number of electrons emerging from the second side in comparison tothe number of electrons introduced at the first side of the plate.

In one particular use of the electron multiplier of the presentinvention a plurality of such grooved plates may be stacked together ora single elongated plate may be spiraled so as to provide for atwo-dimensional electron multiplier. Specifically, the two-dimensionaltype of electron multiplier may be used in a structure such as an imageintensifier, since it would be desirable to provide for an increase inintensity of a two-dimensional image. Also, in the construction of theelectron multiplier of the present invention an accelerating field maybe provided so as to compel the movement of the electrons in the properdirection along the grooves. The use of the accelerating field insuressuccessive collisions of the electrons with the secondary emissionmaterial at successive points along the grooves.

The prior art electron multipliers were constructed of a plurality ofsmall tubes of insulating material such as glass to form a plurality ofelectron channels. For example, in the prior art, small tubes of glasswould be stacked together to provide for a two-dimensional electronmultiplier. The size of the channels would be reduced by 3,519,870Patented July 7, 1970 progressively drawing the tubes smaller andsmaller so as to reduce the dimensions of the tubes and provide for agreat number of electron channels in a small area. The openings throughthe glass tubes were, therefore, very small and it was extremelydifiicult to deposit secondary emission material on the interior surfaceof the tubes.

Since it was difficult to deposit secondary emission material on theinterior surface of the tubes, the prior art electron multipliers wereconstructed of lead glass and the lead glass was processed by a hydrogenreduction of the interior surface of the tubes so as to produce a layerof secondary emission material on the interior surface of the tubes.However, it is to be appreciated that it is difiicult to provide forsuch a hydrogen reduction of the interior surface of the lead glasstubes and, moreover, it is diflicult to provide for uniformity of thelayer of secondary emission material. A non-uniformity of the layer ofsecondary emission material between difierent electron channels canresult in errors in the output from the electron multiplier.

The prior art electron multipliers using a plurality of small tubes wereextremely expensive to construct and did not provide for uniformresults. Another limitation with the prior art electron multipliers ofthe type using a plurality of the small tubes was that the electronmultipliers were limited to the use of a layer of secondary emissionmaterial which was produced by hydrogen reduction and it was notpossible to provide for the deposition of other secondary emissionmaterials which have secondary emission ratios higher than that providedby the hydrogen reduction.

The present invention uses a plate of insulating material having aplurality of grooves along at least one surface of the plate. Thegrooves are open so that it is simple to perform further operations onthe interior of the grooves. For example, the grooved plate ofinsulating material may be constructed of a lead glass and the plate oflead glass is processed by hydrogen reduction, so as to provide for alayer of secondary emission material covering the walls of the grooves.Since the grooves are open, it is much simpler to control the uniformityof the layer of secondary emission material formed by the hydrogenreduction process.

However, one of the significant advantages of the electron multiplier ofthe present invention is that other secondary emission materials may bedeposited to cover the walls of the grooves so as to provide for thelayer of secondary emission material. Also, since the grooves are open,the secondary emission material may be deposited uniformly throughoutthe length of the grooves. It is, therefore, possible with the presentinvention to provide for the deposition of materials having relativelyhigh secondary emission ratios in place of the lower secondary emissionratio materials used in the prior art electron multipliers. For example,with the present invention, materials such as magnesium oxide may beused for the layer of secondary emission material so as to provide forelectron channels having relatively high multiplication factors.

Not only does the use of the grooved plates allow for the deposition ofmaterials so as to provide for an improved performance in the electronmultiplier of the present invention, but, in addition, the use of thegrooved plates provides for a much simpler construction of an electronmultiplier and allows for a greater freedom in the manufacturing of theelectron multiplier of the present invention. The electron multiplier ofthe present invention, therefore, is much simpler to build than priorart electron multipliers and is less expensive than such prior artelectron multipliers.

As indicated above, a plurality of the grooved plates may be stacked ora single grooved plate may be spiraled so as to form a two-dimensionalelectron multiplier. Thev construction of the two-dimensional electronmultiplier of the present invention is much simpler than the use of aplurality of small tubes as with the prior art electron multipliers. Thestacking or spiraling of the grooved plate is a much simplerconstruction for the electron multiplier of the present invention whencompared with the prior art electron multipliers. The simplerconstruction for the electron multiplier of the present invention leadsto a reduction in cost of the electron multiplier of the presentinvention over the prior art electron multipliers.

An accelerating field may also be used in the electron multiplier of thepresent invention by providing a difference in potential across theopposite sides of the grooved plate. The secondary emission material maybe constructed to have a controlled high resistance or a separate layerof material having a controlled high resistance may be deposited betweenthe surface of the grooved plate and the secondary emission material.The controlled high resistance provides for a uniform drop in voltagealong the lenth of the grooves due to the difference in potentialapplied across the sides of the grooved plate and the uniform drop involtage produces a uniform electric field in the grooves parallel to thesurface of the grooves.

Contact areas may be included at the sides of the grooved plate so as toprovide for attachment points for the voltage potential. The electricfield operates to accelerate the electrons within the grooves whichserve as electron channels and the electric field insures the movementof the electrons in the proper direction so as to provide for amultiplication of electrons by successive contacts between the electronsand the secondary emission material.

When the electron multiplier of the present invention is being used aspart of an image intensifier, the electrons may be introduced to thefirst side of the grooves from a source of electrons such as a plate ofphoto-emissive material. The plate of photo-emissive material mayreceive an image which is to be intensified so that the electrons whichare introduced to the grooves are in accordance with the image. Theelectrons in accordance with the image are multiplied as they progressalong the grooves and the electrons emerge at the second opposite sideof the grooves.

The electrons from the second side of the grooves are multiplied inaccordance with the particular multiplication factor of the electronmultiplier which depends upon various factors such as the secondaryemission material, the number of contacts between the electrons and thesecondary emission material, etc. The electrons from the second side ofthe grooves which emerge are then directed to a screen such as afluorescent screen so as to provide for an image on the screen having anintensity greater than the intensity of the original image. The electronmultiplier may, therefore, be used as an image intensifier so as toprovide for an intensification of a weak or dim image.

The present invention is, therefore, directed to a new construction foran electron multiplier which provides for improved performance overelectron multipliers of the prior art. In addition, the electronmultipler of the present invention may be produced with a reduced costover prior art electron multipliers. A greater understanding of theelectron multiplier of the present invention may be had 'with referenceto the further description of the invention and with reference to thefollowing drawings wherein:

FIG. 1 is an illustration of an image intensifier using an electronmultiplier;

FIG. 2 is an illustration of a single electron channel of an electronmultiplier illustrating the multiplication of the electrons;

FIG. 3 is a first embodiment of an electron multiplier constructed inaccordance with the present invention;

FIG. 3a is an enlarged fragmentary view of a portion of the electronmultiplier of FIG. 3;

FIG. 4 is a second embodiment of an electron multiplier constructed inaccordance with the present invention;

FIG. 4a is an enlarged fragmentary view of a portion of the electronmultiplier of FIG. 4;

FIG. 5 is a third embodiment of an electron multiplier constructed inaccordance with the present invention;

FIG. 5a is an enlarged fragmentary view of a portion of the electronmultiplier of FIG. 5;

FIGS. 6a, 6b and 6c illustrate three steps in the production of anelectron multiplier constructed in accordance with the presentinvention;

FIG. 7 diagrams a process which may be used to produce an electronmultiplier from a physical structure such as shown in FIG. 60; and

FIG. 8 illustrates a technique for mass producing an electron multiplierconstructed in accordance with the present invention.

In FIG. 1, an image intensifier using an electron multiplier isillustrated. The image intensifier 10 is used to intensify an image 12.A first plate 14 of translucent insulating material supports a sheet ofphoto-emissive material 16. The photo-emissive material 16 receives theimage 12 and produces electrons at particular positions along the sheetof photo-emissive material in accordance with the intensity of the imageat various positions within the image.

The electrons from the photo-emissive sheet of material 16 are directedthrough a second plate of insulating material 18 and toward an electronmultiplier 20. The electron multiplier includes a plurality of channels,each having secondary emission material so as to provide for amultiplication of the electrons in a manner to be described later. Theelectron multiplier also includes conductive coatings 22 and 24 oneither side of the electron multiplier.

After the electrons emerge from the electron multiplier 20, they passthrough a plate of insulating material 26. The plate of insulatingmaterial 26 supports a sheet of fluorescent material 28 which serves asa fluorescent screen. A second plate 30 of translucent insulatingmaterial serves to protect the fluorescent material 28. As can be seenin FIG. 1, the original image 12 is reproduced by the fluorescentmaterial 2 8 as a new image 32, and the iliilage 32 has a greaterintensity than the original image The image intensifier 10 of FIG. 1also includes a power supply 34 which provides a plurality of voltagepotentials which are connected to the sheet of photoemissive material16, the contact areas 22 and 24, and the sheet of fluorescent material28. The potential on the sheet of photo-emissive material 16 is lessthan the potential on the contact area 22 so as to provide anaccelerating field for the electrons produced by the photo-emissivematerial 16. The accelerating field produced by the voltage potentialbetween the contact area 22 and the photo-emissive material compels themovement of the electrons produced by the photo-emissive material 16towards the electron multiplier 20. Also, the potential on the sheet ofconductive material 22 is greater than the potential on the sheet ofconductive material 24 so as to produce an accelerating field within theelectron channels to compel movement of the electrons within the variouselectron channels contained -in the electron multiplier 20. Finally, thepotential on the sheet of conductive material 24 is less than thepotential on the sheet of fluorescent material 28 so as to produce anaccelerating field to compel movement of the multiplied electronstowards the sheet of fluorescent material 28.

FIG. 2 illustrates a single one of the electron channels of an electronmultiplier such as the electron multiplier 20 of FIG. 1. In FIG. 2, thecontact material 22 and 24 is shown on opposite sides of the electronmultiplier and it can be seen that the contact material does not coverthe various openings for the individual channels in the electronmultiplier 20. The electron multiplier 20 also contains a layer ofsecondary emission material 36 so as to provide for a multiplication ofthe electrons. Depending on the particular configuration of the electronchannel, the secondary emission material 36 may completely surround theelectron channel or the electron secondary emission materials 36 maypartially surround the electron channel.

As an illustration of the operation of the electron mul tiplier 20 andin particular the operation of a single one of the electron channels ofthe electron multiplier, a single electron is shown entering theelectron channel on the first side of the electron multiplier 20. It isassumed that the secondary emission material 36 has a secondary emissionratio of 2; that is, for every electron which strikes the surface of thesecondary emission material 36, two electrons are released from thesecondary emission material. Therefore, as shown in FIG. 2, as eachelectron strikes the secondary emission material 36, two electrons areshown to be released. The single electron shown entering the electronchannel in FIG. 2 strikes the secondary emission material 36 andreleases two electrons. These two electrons also strike the secondaryemission material 36 and each electron releases two electrons to producea total of four electrons. The four electrons in turn strike thesecondary emission material to produce eight electrons.

As shown in FIG. 2, a large number of electrons are shown to emerge fromthe side of electron multiplier 20 containing the conductive material24. It is to be appreciated, however, that in the actual operation ofthe electrofin multiplier, a large number of collisions of the electronsoccur along the length of the electron channel so as to provide manymore electrons than those shown emerging from the electron channel ofFIG. 2. Also, it is to be appreciated that secondary emission materialmay be used which has a higher secondary emission ratio than thatassumed for the illustration of FIG. 2. Therefore, it is possible toobtain an extremely large multiplication of the electrons.

FIG. 3 illustrates a first embodiemnt of an electron multiplierconstructed in accordance with the present invention which may be usedas part of the image intensifier of FIG. 1. FIG. 3a is an enlargedfragmentary view of a portion of the electron multiplier of FIG. 3. Theelectron multiplier of FIG. 3 includes a plurality of plates ofinsulating material 100. The plates 100 are stacked together so as toform a composite electron multiplier structure. Each of the platescontains a plurality of parallel grooves 102 on at least one surface ofthe plate. The grooves 102 are lined with a layer of secondary emissionmaterial 104 which is more clearly shown in FIG. 3a. The secondaryemission material 104 is used to provide for the multiplication of theelectrons as they pass through the grooves 102 and strike the secondaryemission material at progressive positions along the grooves 102.

The electron multiplier of FIG. 3 may also include a layer of material106 which has a controlled high resistivity as shown in FIG. 3a. Thelayer of controlled high resistivity material 106 would be connected,for example, to contact areas such as contact areas 22 and 24 shown inFIG. 1, so that the difference in voltage potential applied to thecontact areas 22 and 24 would have a uniform voltage drop throughout thegrooves 102 shown in FIG. 3, due to the controlled high resistivity ofthe layer 106. The uniform voltage drop would provide for a uniformelectric field within the grooves 102. The uniform electric field isparallel to the walls of the grooves 102 and is an accelerating field toinsure that the electrons flow in the proper direction while making thesuccessive contacts with the secondary emission material 104. It is tobe appreciated that the secondary emission material 104 may itself havea controlled high resistivity so as to eliminate the necessity for anadditional layer of controlled high resistivity material.

In the embodiment of the electron multiplier shown in FIG. 3 and FIG.3a, it can be seen that the plates have the grooves 102 open along onesurface before the plates are stacked. It can, therefore, be seen thatit is easy to control the deposition of the layers 104 and 106 since thegrooves are open along the one surface. It is, therefore, possible touse secondary emission materials, for example, materials such asmagnesium oxide, which have a high secondary emission ratio. It is alsoto be appreciated that the plates 100 may be composed of lead glass suchas the prior art electron multipliers and the lead glass may besubjected to a hydrogen reduction so as to form the layer of secondaryemission material covering the surface of the grooves 102. However,since the grooves are open along the one surface, it is easier tocontrol the uniformity of the layer formed by the hydrogen reductionthan the prior art electron multipliers.

FIGS. 4 and 4a illustrate a second embodiment of an electron multiplierconstructed in accordance with the present invention. FIG. 4a is anenlarged fragmentary view of a portion of FIG. 4. In FIG. 4, a pluralityof plates have grooves 152 on one surface of the plates and grooves 154on the other surface of the plates. As shown in FIG. 4a, the grooves15.2 and 154 may contain dual layers including secondary emissionmaterial 156 and a controlled high resistivity material 108.

It is to be appreciated that the embodiment of FIG. 4 is more difficultto stack since the grooves 152 and 154 in adjacent plates must beaccurately aligned whereas the plates 100 of the embodiment of FIG. 3 donot have to have the grooves 102 aligned. The embodiment of FIG. 4 alsohas an electron channel having secondary emission material completelysurrounding the electrons whereas the embodiment of FIG. 3 has theelectron channel having secondary emission material only partiallysurrounding the electrons. However, the simplicity of the constructionof the embodiment of FIG. 3 makes the structure such as shown in FIG. 3a preferred embodiment of the invention. It is also to be appreciatedthat secondary emission material may be deposited on the flat surface ofthe plates 100 shown in FIG. 3 so that the electron channel hassecondary emission material completely surrounding the electrons.

FIG. 5 illustrates a third embodiment of the invention including asingle plate of insulating material 200 spiraled so as to form atwo-dimensional electron multiplier. The plate 200 includes grooves 202spaced along the plate. As shown in FIG. 5a, the grooves 202 may have afirst layer of secondary emission material 204 and a second layer ofcontrolled high resistivity material 206. It is to be appreciated asindicated above that the secondary emission material itself may have acontrolled high resistivity so as to eliminate the second layer ofcontrolled high resistivity material. Also, as indicated above, theplates may be constructed of lead glass so that the secondary emissionmate rial may be formed by a hydrogen reduction of the lead glass.However, the present invention also has the capability of usingsecondary emission materials which may be deposited within the groovesand which provide a high secondary emission ratio.

The embodiment of FIG. 5 is relatively simple in construction since theplate 200 is merely spiraled so as to form the two-dimensional electronmultiplier. Also, in the embodiment shown in FIG. 5, wherein the groovesare contained on the inside surfaces of the plate 200, the side walls ofthe grooves flex inward as. the plate is spiraled so as to provide for amore complete encircling of the grooves which serve as electronchannels.

The electron multipliers as shown in FIGS, 3, 4 and 5 are simpler inconstruction than the prior art electron multipliers and result in agreat reduction in cost for e1ectron multipliers of FIGS. 3, 4 and 5over the prior art electron multipliers. In addition, since the electronchannels are open along one surface prior to stacking or spiraling, itis possible to use secondary emission material which is deposited withinthe channels, whereas the prior art electron multipliers which use smalltubes could not have the secondary emission material deposited withinthe tubes. The electron multiplier of the present invention, therefore,provides for an improved performance over the electron multipliers ofthe prior art. The electron multiplier of the present invention may beconstructed by various methods and, as examples, FIGS. 6, 7 and 8illustrate two methods of constructing the electron multipliers.

In FIGS. 6a, 6b and 6c, a single sheet of insulating material is showntransformed to a grooved plate. In FIG. 6a, an elongated flat plate ofinsulating material 250 is shown. The plate of insulating material 250may be composed of material such as glass. In FIG. 6b the plate 250 iscoated with a layer of photo-sensitive material 252 and a pattern 254 isdeveloped on the photo-sensitive material. FIG. 66 shows the plate 250etched away in accordance with the pattern 254 shown in FIG. 6b so as toproduce a plurality of grooves 256. The plate 250 containing the grooves256 which serve as electron channels is further processed as shown bythe method of FIG. 7.

In FIG. 7, the plate 250 first has an electrode material such aschromium or other suitable metal evaporated with the grooves by a firststep 300. The evaporative process produces a layer of an electrode suchas chromium or other suitable metal within the grooves. The electrodematerial is then oxidized by a second step 302 so as to provide for acontrolled high resistivity of the electrode material. The material suchas chromium oxide, therefore, provides for a controlled resistivity soas to produce a uniform electric field in the grooves 256 when adifference in potential is applied across the ends of the grooves. Theuniform electric field acts as an accelerating field within the grooves.

A layer of prospective secondary emission material is then evaporativelydeposited on top of the layer of electrode material in a third step 304.For example, magnesium may be deposited on top of the electrodematerial. A fourth step 306 is to oxidize the prospective secondarymaterial so as to produce the secondary emission material. For example,if magnesiumris used, the magnesium is oxidized to magnesium oxide whichhas a high secondary emission ratio.

A fifth step 308 in the method of FIG. 7 is to stack the various plates250 together so that the plurality of grooves 256 which now includelayers of controlled high resistivity material and secondary emissionmaterial form a two-dimensional array of electron channels. A final step310 is to metalize the ends of the stack of plates so as to producecontact areas. The contact areas receive the voltage potential so as toproduce the accelerating field within the grooves. The metalized endswould be similar to the metalized ends 22 and 24 shown in FIG. 1.

The methods illustrated in FIGS. 6 and 7 may be used to produce electronmultipliers of the type shown in FIGS. 3 and 4. It is to be appreciatedthat the plate 250 shown in FIG. 6a may be much longer than that shownand the plate may then be spiraled to produce an electron multiplier asshown in FIG. 5.

FIG. 8 illustrates a method for mass producing electron multipliers ofthe type shown in FIGS. 3, 4 and 5. In FIG. 8, a roll of insulatingmaterial 350 is unrolled and passed through an oven 352 so as to softenthe material 350. The insulating material 350, for example, may beglass. The softened insulating material 350 is then corrugated by astructure including a large wheel 354 having a smooth surface and asmaller corrugated wheel 356. The wheel 356 produces a plurality ofgrooves 358 in the surface of the material 350. The grooved insulatingmaterial 350 after passing through the Wheel 356 is similar to thegrooved structure shown in FIG. 60.

The grooved insulating material 350 passes through a first evaporator360 which evaporatively deposits a layer of electrode material. Anoxidizer 362 oxidizes the electrode material to produce a layer ofcontrolled high resistivity material in the grooves. The controlled highresistivity material may be chromium oxide. The grooved insulatingmateral then passes through a second evaporator 364 whch evaporates aprospective secondary emission material. Finally, a second oxidizer 366oxidizes the prospective secondary emission material to produce a layerof secondary emission material in the grooves. The secondary emissionmaterial, for example, may be magnesium oxide.

The grooved material now has a plurality of grooves which contain layersof secondary emission material and high resistivity material so as toform the electron multiplier. For example, as shown at position 368, thematerial 350 as it passes out of the oxidizer 366 may be rolled directlyto form an electron multiplier of the type shown in FIG. 5. Also, thematerial 350 as it passes out of the oxidizer 366 may be chopped intosmaller sections which in turn may be stacked to form an electronmultiplier of the type shown in FIG. 3. It is to be appreciated that theparticular manner in which the material 350 is handled after theoxidizer 366 would be a matter of choice.

The present invention is, therefore, directed to a new simpleconstruction for an electron multiplier which is less expensive thanprior art electron multipliers and which provides for an improvedperformance over prior art electron multipliers. The performance of theelectron multiplier of the present invention is improved in part becausesecondary emission materials may be used having a higher secondaryemission ratio than those used in the prior art electron multipliers.

The present invention has been described with reference to particularembodiments and, in addition, two illustrative methods have been shownfor producing the electron multipliers of the present invention. Inaddition, it has been indicated that the electron multiplier of thepresent invention may be used as part of an image intensifier so as toprovide for an increase in intensity of a dim image.

It is to be appreciated that although the invention has been describedwith reference to particular embodiments, various adaptations andmodifications may be made. The invention, therefore, is only to belimited by the appended claims.

What is claimed is:

1. An electron multiplier comprising:

(a) a roll of insulating strip material having a plurality of parallelgrooves forming a plurality of electron channels on one surface of thestrip material extending from a first side of the strip material to asecond side of the strip material, said roll forming a spiral with thelands between said grooves in contact with the second surface of adifferent turn of said spiraled strip material to close said electronchannels intermediate said first and second sides,

(b) means for producing an accelerating electric field within thegrooves from the first side of the strip material to the second side ofthe strip material for accelerating electrons introduced into thegrooves from the first side of the strip material to the second side ofsaid strip material, said means comprising contact areas at the firstside of the strip material and the second side of the strip material andan electrical potential coupled to said contact areas, and

(c) a layer of secondary emission material having controlled highresistivity covering the surface of the grooves for providing amultiplication of the number of electrons introduced into the grooves atthe first side of the strip material to the number of electrons emergingat the second side of the strip material in accordance with theelectrons striking the secondary emission material at successive pointsalong the grooves.

9 2. The electron multiplier according to claim 1, and 3,128,408 whereinthe secondary emission material having controlled 3,182,221 highresistivity is magnesium oxide. 3,341,730 3,343,025 References Cited3,387,137 5 2160799 UNITED STATES PATENTS 3244922 2,225,786 12/1940Langenwalter et a1. 313-105 1 1 1 2,232,900 2/1941 Brewer 313-1052,674,661 4/1954 Law 313-105 10 Goodrich et a1. 313-103 X Poor 313-103Goodrich et a1. 313-104 X Ignatowski et a1. 313-105 Adams 313-104 X Teal313-95 Wolfgang 313-95 Wolfgang; et al. 313-104 X ROBERT SEGAL, PrimaryExaminer

